The effect of end season drought stress on the chlorophyll content, chlorophyll fluorescence parameters and yield in maize cultivars

The drought is the most important limiting factor of the agricultural plants production in Iran and the world. Much of the Iranian lands are classified as arid and semi arid areas. To evaluate the effect of drought stress of the last season in 2007 to 2008 on the chlorophyll fluorescence, chlorophyll content of leaf and having the tolerance of five maize genotypes, this experiment was done in a randomized complete block design in four replications in two conditions. Experiment carried out from 2008 to 2010 and in two agricultural years in Ardabil and the farming lands of Arjestan area located in 16 km of northwest of Ardabil. The results of analysis of variance showed the significant differences among genotypes as well as all the traits which were evaluated in two years of testing that showed the genetic richness of cultivars. The result of the mean comparisons showed with applying the stress on the amount of  F0 was added but the amount of chlorophyll and the ratio of  Fv/Fm and ultimately the amount of grain yield was reduced that shows a negative effect of the drought stress on the chlorophyll parameters. The studies showed that the cultivars having the more chlorophyll are also stress tolerant according to the results, single cross genotype having the highest rate of chlorophyll and chlorophyll fluorescence parameters as the stress tolerant genotype were selected. Finally it was found that due to high correlation between the Fv/Fm ratio and also the leaf chlorophyll with the yield (respectively: R = 0.88** and R = 0.745**), these parameters can be used to assess the stress intensity and selecting the most tolerant genotype.   Key words: Arjestan, Ardabil, drought stress, maize, chlorophyll fluorescence.